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Calculate mean arterial pressure from systolic and diastolic blood pressure. MAP represents the average pressure in the arteries during one cardiac cycle and is a key indicator of tissue perfusion.
• MAP is critical for assessing adequate organ perfusion
• Minimum MAP of 65 mmHg generally required for organ perfusion
• Target MAP varies by clinical condition and patient factors
• Use in context of overall hemodynamic assessment
• Consider individual patient history and comorbidities
Formula: MAP = Diastolic BP + ⅓(Systolic BP - Diastolic BP)
Alternative: MAP = (2 × Diastolic BP + Systolic BP) / 3
| Clinical Condition | Target MAP (mmHg) | Rationale |
|---|---|---|
| General Critical Care | ≥ 65 | Minimum for adequate organ perfusion |
| Septic Shock | 65-70 | Initial target per Surviving Sepsis guidelines |
| Chronic Hypertension | 80-85 | Higher target to maintain perfusion (shifted autoregulation) |
| Traumatic Brain Injury | 80-90 | Maintain adequate CPP (CPP = MAP - ICP) |
| Spinal Cord Injury | 85-90 | Enhance spinal cord perfusion in acute phase (first 7 days) |
| Acute Kidney Injury | 65-75 | Maintain renal perfusion pressure |
| Hemorrhagic Shock | 60-65 (permissive) | Until hemorrhage control (avoid disrupting clot) |
| Post-Cardiac Surgery | 70-80 | Ensure coronary and systemic perfusion |
| Pregnancy (severe preeclampsia) | < 125 | Prevent maternal complications while maintaining placental perfusion |
Mean arterial pressure (MAP) represents the average pressure in the arterial system during one complete cardiac cycle. It's weighted more toward diastolic pressure because diastole lasts approximately twice as long as systole. MAP is a better indicator of tissue perfusion than systolic blood pressure alone because it accounts for the continuous forward flow of blood through the cardiac cycle.
The classic formula MAP = DBP + ⅓(SBP - DBP) assumes a heart rate of 60 bpm. At higher heart rates, diastole shortens proportionally more than systole, so the weighting changes slightly. However, the standard formula remains clinically useful for most situations.
Cerebral Autoregulation:
Renal Autoregulation:
Coronary Perfusion:
Initial Resuscitation:
Septic Shock:
Hemorrhagic Shock:
Pulse pressure = Systolic BP - Diastolic BP. Normal range is 25-60 mmHg (typically ~40 mmHg).
Narrow Pulse Pressure (< 25 mmHg):
Wide Pulse Pressure (> 60 mmHg):
Increase MAP:
Decrease MAP:
MAP better represents the perfusion pressure delivered to organs throughout the entire cardiac cycle. Systolic pressure is just a brief peak, while MAP accounts for the continuous driving force for blood flow. Organs need sustained perfusion pressure, not just momentary spikes. Additionally, MAP is less influenced by measurement artifacts and waveform distortion that can affect systolic readings, especially with arterial lines.
Automated cuff measurements calculate MAP from an algorithm using systolic and diastolic readings, while arterial lines directly measure and integrate the arterial waveform over time. Arterial line MAP is generally more accurate, especially in shock states where cuff measurements may be unreliable. However, arterial line systolic pressures tend to be 5-20 mmHg higher than cuff readings due to waveform amplification in peripheral arteries (MAP stays similar). Use arterial line for continuous accurate monitoring in critically ill patients.
Maybe. Chronic hypertension shifts the autoregulation curve rightward, meaning these patients may need higher MAP to maintain organ perfusion. The SEPSISPAM trial showed chronic hypertensives in septic shock had less kidney injury with MAP target 80-85 vs 65-70 mmHg. However, higher targets increase risk of arrhythmias and excessive vasopressor use. Consider starting at MAP 65-70 for all patients, then titrating up if signs of inadequate perfusion despite meeting this target. Individual patient history matters more than age alone.
MAP is just one piece of the puzzle. Also monitor: 1) Lactate levels and clearance (elevated lactate suggests tissue hypoperfusion), 2) Urine output (target ≥ 0.5 mL/kg/hr), 3) Mental status changes, 4) Skin perfusion (capillary refill, temperature, mottling), 5) Mixed venous oxygen saturation (ScvO₂), 6) Cardiac output/index if available, 7) Base deficit/pH. Don't treat the number—treat the patient. A "good" MAP with persistent hyperlactatemia or oliguria indicates inadequate resuscitation.
Start with fluid resuscitation if patient is volume-responsive (hypovolemia). Give crystalloid boluses (500-1000 mL) and assess response using dynamic parameters like pulse pressure variation or passive leg raise. Once fluid-optimized but MAP still low, add vasopressors. In distributive shock (sepsis), you'll often need both. Don't delay vasopressors if patient profoundly hypotensive despite fluids— start norepinephrine early. Excessive fluids without vasopressors can worsen outcomes. In cardiogenic shock, fluids may be harmful; consider inotropes/vasopressors earlier.
Norepinephrine is first-line for most shock states (septic, hypovolemic). It increases MAP through both vasoconstriction (alpha-1) and modest cardiac stimulation (beta-1). Vasopressin can be added as second-line agent. Epinephrine is option for refractory shock or cardiac arrest. Phenylephrine (pure vasoconstrictor) useful when tachycardia is concern. Dopamine rarely used now due to increased arrhythmias. In cardiogenic shock, consider dobutamine (inotrope). The choice depends on underlying pathophysiology—match the drug to the problem (low SVR vs low CO vs both).
Cerebral perfusion pressure (CPP) = MAP - ICP (intracranial pressure). Target CPP is typically 60-70 mmHg in traumatic brain injury. If ICP is elevated (e.g., 20 mmHg), you'd need MAP of 80-90 mmHg to maintain adequate CPP. Monitor both MAP and ICP when available. Increase MAP or decrease ICP to improve CPP. Avoid excessive MAP that could worsen cerebral edema. The goal is adequate cerebral blood flow without exacerbating injury. See CPP calculator for detailed calculations.
Yes. Excessive MAP increases cardiac workload (higher afterload), can cause or worsen pulmonary edema, increases risk of hemorrhagic complications (intracranial hemorrhage, bleeding from vascular injuries), may impair microcirculation through excessive vasoconstriction, and increases risk of arrhythmias from high-dose vasopressors. In most critically ill patients, MAP > 110 mmHg is unnecessarily high. Exceptions exist (active hemorrhage requiring higher BP for hemostasis), but generally avoid excessive MAP. Titrate to lowest MAP that maintains adequate perfusion.